Scanning electron microscope observation of canal cleanliness.

The aim of this study was to evaluate the cleansing efficiency of three root canal preparation techniques. The distal root canals of mandibular molars, divided into three groups of four teeth each, were prepared according to the following techniques: manual (serial), ultrasonic (Cavi-Endo), and automated (Canal Finder). The canal wall surfaces were examined under a scanning electron microscope at three levels. No preparation technique was found to result in any characteristic microscopic features that distinguished it from the other techniques. The lack of such differences makes it impossible to establish objective criteria for comparing these techniques in terms of root canal cleanliness. It was established that even canals that appeared to be clean included areas coated with smear layer and having uninstrumented areas and even pulpal tissue debris.